1. Field of the Invention
This invention relates to electric fan assemblies and in particular, to combined heating and cooling domestic fan assemblies.
2. Description of Prior Art
Domestic electric cooling fans traditionally fall into three distinct types:
(a) slowly rotating ceiling sweep fans, having large blades,
(b) oscillating fans comprising small high speed fan blade assemblies mounted in a pivoting head assembly, and
(c) box fans incorporating a high speed fan blade assembly and a rotating louvre to provide a gyratory air current.
Fans of the kind described above are effective in moving large volumes of air either by use of large diameter slowly moving fan blades or by the use of faster, small diameter fan blades.
Whilst fans of the above kind adequately cater for the requirement as cooling fans, such fans are not suitable for use as heating fans. Conventional heating fans or convection heaters incorporate electrical heating coils positioned adjacent either a centrifugal, axial, or tangential flow fan blade assembly. It is, however, important that the velocity of the exeunt air is not too large because even though a fan operating at high speed will transmit as much heat to the surroundings as a slow running fan the velocity of air tends to produce a rather cool and draughty effect and for this reason, conventional heating fans operate at low flow rates to ensure that the air leaving the fan is noticeably hot.
Another problem with heating fans is caused by the tendency of hot air to rise. As an electric fan is used in a closed room, the heat rises to collect at the ceiling and after a period of time, a stratification of the atmosphere in the room takes place forming layers of different temperatures, the highest temperature being at the ceiling, with a gradual decrease in temperature to the floor. The result of this stratification is that the upper parts of the room may be unnecessarily hot whilst the lower part of the room, particularly at feet level, is many degrees cooler. This results in a waste of energy because the occupants of the room, particularly if seated, do not feel the effect of the majority of the heat produced by the fan, and moreover there is frequently a substantial degree of heat loss through the ceiling.